88 research outputs found
Cloning of Gaussian states by linear optics
No full textWe analyze in details a scheme for cloning of Gaussian states based on linear optical components and homodyne detection recently demonstrated by Andersen [Phys. Rev. Lett. 94, 240503 (2005)]. The input-output fidelity is evaluated for a generic (pure or mixed) Gaussian state taking into account the effect of nonunit quantum efficiency and unbalanced mode mixing. In addition, since in most quantum information protocols the covariance matrix of the set of input states is not perfectly known, we evaluate the average cloning fidelity for classes of Gaussian states with the degree of squeezing and the number of thermal photons being only partially known
Optimal cloning of coherent states by linear optics
No full textWe describe an optical scheme for optimal Gaussian n → m cloning of coherent states. The scheme, which generalizes a recently demonstrated scheme for 1 → 2 cloning, involves only linear optical components and homodyne detection
Ab initio quantum-enhanced optical phase estimation using real-time feedback control
No full textOptical phase estimation is a vital measurement strategy that is used to perform accurate measurements of various physical quantities including length, velocity and displacements(1,2). The precision of such measurements can be greatly enhanced by the use of entangled or squeezed states of light as demonstrated in a variety of different optical systems(3-8). Most of these accounts, however, deal with the measurement of a very small shift of an already known phase, which is in stark contrast to ab initio phase estimation where the initial phase is unknown(9-12). Here, we report on the realization of a quantum-enhanced and fully deterministic ab initio phase estimation protocol based on real-time feedback control. Using robust squeezed states of light combined with a real-time Bayesian adaptive estimation algorithm, we demonstrate deterministic phase estimation with a precision beyond the quantum shot noise limit. The demonstrated protocol opens up new opportunities for quantum microscopy, quantum metrology and quantum information processing
Demonstration of deterministic and high fidelity squeezing of quantum information
No full textBy employing a recent proposal [R. Filip, P. Marek, and U.L. Andersen, Phys. Rev. A 71, 042308 (2005)] we experimentally demonstrate a universal, deterministic, and high-fidelity squeezing transformation of an optical field. It relies only on linear optics, homodyne detection, feedforward, and an ancillary squeezed vacuum state, thus direct interaction between a strong pump and the quantum state is circumvented. We demonstrate three different squeezing levels for a coherent state input. This scheme is highly suitable for the fault-tolerant squeezing transformation in a continuous variable quantum computer
Diurnal variations of serum erythropoietin at sea level and altitude
No full textThis study tested the hypothesis that the diurnal variations of serum-erythropoietin concentration (serum-EPO) observed in normoxia also exist in hypoxia. The study also attempted to investigate the regulation of EPO production during sustained hypoxia. Nine subjects were investigated at sea level and during 4 days at an altitude of 4350 m. Median sea level serum-EPO concentration was 6 (range 6-13) U.l-1. Serum-EPO concentration increased after 18 and 42 h at altitude, [58 (range 39-240) and 54 (range 36-340) U.l-1, respectively], and then decreased after 64 and 88 h at altitude [34 (range 18-290) and 31 (range 17-104) U.l-1, respectively]. These changes of serum-EPO concentration were correlated to the changes in arterial blood oxygen saturation (r = -0.60, P = 0.0009), pH (r = 0.67, P = 0.003), and in-vivo venous blood oxygen half saturation tension (r = -0.68, P = 0.004) but not to the changes in 2, 3 diphosphoglycerate. After 64 h at altitude, six of the nine subjects had down-regulated their serum-EPO concentrations so that median values were three times above those at sea level. These six subjects had significant diurnal variations of serum-EPO concentration at sea level; the nadir occurred between 0800-1600 hours [6 (range 4-13) U.l-1], and peak concentrations occurred at 0400 hours [9 (range 8-14) U.l-1, P = 0.02]. After 64 h at altitude, the subjects had significant diurnal variations of serum-EPO concentration; the nadir occurred at 1600 hours [20 (range 16-26) U.l-1], and peak concentrations occurred at 0400 hours [31 (range 20-38) U.l-1, P = 0.02]. This study demonstrated diurnal variations of serum-EPO concentration in normoxia and hypoxia, with comparable time courses of median values. The results also suggested that EPO production at altitude is influenced by changes in pH and haemoglobin oxygen affinity
John in Canterbury.
No full textLower centre (l.c.) with brush: McCahon August ’59; u.l. - c.r. with brush: God, it is all dark. The heart beat but there is no answering hark of a hearer and no-one to speak; l.r. with brush: John in Canterbury; verso: Colin McCahon No 36 August 59 John in Canterbury Butex 30 gns
Lowering the pump power requirement for squeezed light generation using a periodically poled crystal
No full textObservations of continuous wave bright squeezed light from an intra-cavity periodically poled KTP second harmonic generator are presented. The experiment includes characterization of the classical as well as the quantum properties of the system
2024 roadmap on magnetic microscopy techniques and their applications in materials science
No full textThe authors acknowledge financial support of the DFG by the Collaborative Research Center SFB 1143 (Project-id 247310070)Christensen D.V., Staub U., Devidas T.R., Kalisky B., Nowack K.C., Webb J.L., Andersen U.L., Huck A., Broadway D.A., Wagner K., Maletinsky P., van der Sar T., Du C.R., Yacoby A., Collomb D., Bending S., Oral A., Hug H.J., Mandru A.-O., Neu V., Schumacher H.W., Sievers S., Saito H., Khajetoorians A.A., Hauptmann N., Baumann S., Eichler A., Degen C.L., McCord J., Vogel M., Fiebig M., Fischer P., Hierro-Rodriguez A., Finizio S., Dhesi S.S., Donnelly C., Büttner F., Kfir O., Hu W., Zayko S., Eisebitt S., Pfau B., Frömter R., Kläui M., Yasin F.S., McMorran B.J., Seki S., Yu X., Lubk A., Wolf D., Pryds N., Makarov D., Poggio M
Planning hydroelectric power plants with the public: A case of organizational and social learning in Mexico
No full textThe standard degree of polarization involves exclusively first-order moments of the Stokes variables. This may be sufficient for most classical problems, but for quantum fields higher-order correlations are crucial. We claim that a complete polarization characterization must involve a whole hierarchy of polarization degrees constructed order by order, as it happens in coherence theory. We present here a second-order degree and determine it experimentally. "2011 Optical Society of America.",,,,,,,,,"http://hdl.handle.net/20.500.12104/43683","http://www.scopus.com/inward/record.url?eid=2-s2.0-84893596041&partnerID=40&md5=8e4b3bc6002c22fa192eafbf1b9fd2d5",,,,,,,,"Optics InfoBase Conference Papers",,,,,,"Scopus",,,,,,,,,,,,"Polarization correlations in quantum optics",,"Conference Paper"
"45456","123456789/35008",,"López, J.A., Instituto de Astronomía, UNAM, Apartado Postal 877, 22800 Ensenada, B.C., Mexico; Rodríguez, L.F., Instituto de Astronomía, UNAM, Apartado Postal 72-3 (Xangari), 58089 Morelia Mich., Mexico; García-Segura, G., Instituto de Astronomía, UNAM, Apartado Postal 877, 22800 Ensenada, B.C., Mexico; Meaburn, J., Jodrell Bank Observatory, U. of Manchester, Lower Withington, Maccles field, Cheshire SK11 9DL, United Kingdom; Franco, J., Instituto de Astronomía, UNAM, Ciudad Universitaria, Apdo. Postal 70-264, México D.F. 04510, Mexico; Vázquez, R., Instituto de Astronomía, UNAM, Apartado Postal 877, 22800 Ensenada, B.C., Mexico; Steffen, W., Instituto de Astronomía Y Meteorología, Universidad de Guadalajara, Apdo. Postal 1-1515, Guadalajara Jal. 44140, Mexico; Miranda, L.F., Instituto de Astrofísica de Andalucía, Apdo. Correos 3004, Granada, E-18080, Spain; Bryce, M., Jodrell Bank Observatory, U. of Manchester, Lower Withington, Maccles field, Cheshire SK11 9DL, United Kingdom",,"Lopez, J.A
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